doc: misc fixes to C domain types

Breathe is not very strict about the types used to reference C domain
objects (ex. referencing a struct using `:c:type:` would work, and vice
versa) but other tooling might be. This commit fixes some of such
incorrectly documented elements.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

doc/develop/api/design_guidelines.rst

@@ -31,7 +31,7 @@ specifying the signature of a callback:
 An exception to providing ``user_data`` as the last parameter may be
 allowed when the callback itself was provided through a structure that
 will be embedded in another structure.  An example of such a case is
-:c:type:`gpio_callback`, normally defined within a data structure
+:c:struct:`gpio_callback`, normally defined within a data structure
 specific to the code that also defines the callback function.  In those
 cases further context can accessed by the callback indirectly by
 :c:macro:`CONTAINER_OF`.
@@ -45,7 +45,7 @@ Examples
     void handle_timeout(struct k_timer *timer)
     { ... }
 
-  The assumption here, as with :c:type:`gpio_callback`, is that the
+  The assumption here, as with :c:struct:`gpio_callback`, is that the
   timer is embedded in a structure reachable from
   :c:macro:`CONTAINER_OF` that can provide additional context to the
   callback.
@@ -62,7 +62,7 @@ Examples
   This provides more complete useful information, including which
   counter channel timed-out and the counter value at which the timeout
   occurred, as well as user context which may or may not be the
-  :c:type:`counter_alarm_cfg` used to register the callback, depending
+  :c:struct:`counter_alarm_cfg` used to register the callback, depending
   on user needs.
 
 Conditional Data and APIs

doc/develop/languages/c/picolibc.rst

@@ -133,7 +133,7 @@ Thread Local Storage
 
 Picolibc uses Thread Local Storage (TLS) (where supported) for data
 which is supposed to remain local to each thread, like
-:c:var:`errno`. This means that TLS support is enabled when using
+:c:macro:`errno`. This means that TLS support is enabled when using
 Picolibc. As all TLS variables are allocated out of the thread stack
 area, this can affect stack size requirements by a few bytes.
 

doc/services/resource_management/index.rst

@@ -80,8 +80,8 @@ state.
    case is asynchronous.  The on-off client structure may be an
    appropriate solution for the generic API.  Where drivers that can
    guarantee synchronous context-independent transitions a driver may
-   use :c:type:`onoff_sync_service` and its supporting API rather than
-   :c:type:`onoff_manager`, with only a small reduction in functionality
+   use :c:struct:`onoff_sync_service` and its supporting API rather than
+   :c:struct:`onoff_manager`, with only a small reduction in functionality
    (primarily no support for the monitor API).
 
 .. doxygengroup:: resource_mgmt_onoff_apis

doc/services/storage/flash_map/flash_map.rst

@@ -78,7 +78,7 @@ Numeric flash area ID is obtained by passing DTS node label to
 :c:macro:`FIXED_PARTITION_ID()`; for example to obtain ID number
 for ``slot0_partition``, user would invoke ``FIXED_PARTITION_ID(slot0_partition)``.
 
-All :c:macro:`FIXED_PARTITION_` macros take DTS node labels as partition
+All :code:`FIXED_PARTITION_*` macros take DTS node labels as partition
 identifiers.
 
 Users do not have to obtain a :c:struct:`flash_area` object pointer